RFR: JDK-8176520: Improve the accuracy of the instance size in hprof heap dumps [v3]

[Kevin Walls]

On Sat, 17 Feb 2024 02:41:20 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> The fix updates heap dumpers to report correct instance size value for HPROF_GC_CLASS_DUMP records (currently it's reported as size of all instance fields)
>> 
>> Testing: tier1, tier2, tier5-svc
>
> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   split test

In the CSR you mention the two places we document the format.
If this goes ahead, we should be updating them to be more specific, to declare that this field is not VM-independent, it has specific VM knowledge, so maybe for HPROF_GC_CLASS_DUMP:

u4         instance size (in bytes)
becomes:
u4         instance size (in bytes, including VM header, padding)

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PR Comment: https://git.openjdk.org/jdk/pull/17855#issuecomment-1961049485